There is an increasing demand for efficient antenna systems capable of operating over large bandwidths in both transmit and receive modes whose dimensional requirements are such that they can be used either as a single horn, a multi-horn primary feed or that can be arrayed to provide high gain secondary patterns. Design conflicts involved are well recognized by antenna engineers. Wideband frequency operations suggest the use of angular or periodic elements such as spirals or arrays of periodic elements. Such devices, however, are inefficient and difficult to instrument at frequencies above 10 GHz.
Single and double ridge waveguides are capable of operating over 3:1 bandwidths. The power capacity and transmission efficiency of ridge waveguides is not as great as for standard rectangular guides but is far better than that associated with coaxial or spiral circuits. The horns of the present invention utilize both single and double ridged waveguide. The system described in this disclosure extends the techniques and means described in the inventor's previously issued patent, U.S. Pat. No. 4,096,482. New mechanisms disclosed herein provide an optimum match within the coaxial-to-ridge waveguide input transformation and utilize a waveguide beyond cut-off guide termination. The radiating apertures of the horns of the present invention are matched to free space by extending the ridges beyond the confines of the waveguide while increasing the gap dimensions in an exponential manner.